Static magnetic frequency tripler



Sept. 19, 1967 Filed Dec. 18, 1964 A. KUSKO v STATIC MAGNETIC FREQUENCY TRIPLER B Sheets-Sheet l Maya 1 INVENTOR.

Sept. 19, 1967 I A. KU SKO 3,343,054

STATIC MAGNETIC FREQUENCY TRIPLER Filed Dec. 18, 1964 l254.54,7a 9/0/ /z 15- 2 Sheets-Sheet 2' 11.14; 0 hzollzo hgg] IZ34-5b789I0/l/2, 5-

INVENTOR. 14L. EXA/VDER Kus/ro United States Patent 0.

3,343,054 STATIC MAGNETIC FREQUENCY TRIPLER Alexander Kusko, Newton, Mass., assignor to Ametek, Inc., a corporation of Delaware Filed Dec. 18, 1964, Ser. No. 419,531 23 Claims. (Cl. 318-42?) ABSTRACT OF THE DISCLOSURE A single phase input-three phase output frequency tripler, comprised of three transformer reactors identically of a first type with one primary and a large secondary, a small secondary with 2:1 secondary turns ratio; three other transformer reactors identically of a second type having two identical primaries and two secondaries, the secondaries of the first type reactor respectively equal in turns numbers to the secondaries of the second type reactor, the ratio of turns in one of the primaries in the second type reactor to the turns in the primary of the first type reactor being 1/ (2 cos- 30); all large secondaries connected in one series as one output phase, all the small secondaries connected in a second series as a second output phase, and the series Scott T connected to provide a three-phase output; a Y or star connection of three sets of primaries in series, each primary series including a primary of one first type reactor and one primary of each of two different second type reactors, the primary The present invention relates generally to the art of frequency multiplication, and more particularly to circuitry and apparatus therefor of the so-called static type,

' that is, not involving moving parts, which further does not essentially require vacuum tube or solid state switching or control devices as generally used in multi-vibrators and like static frequency multipliers.

Specifically, the invention is directed to improvements in apparatus and circuitry for static magnetic frequency multipliers of a type, which has been denominated a transformer type, comprised basically of a plurality of transformers with a set of series-connected secondaries for each of one or more phases of output, and primaries so connected and receiving energizing currents of differing phase relationships and having appropriately different numbers of turns to provide the desired output.

Static magnetic frequency multipliers of this type are long old in the art, varying in physical forms and in manner of interconnection in overall circuitry. Thus, publications by E. Friedlander, in Electrical Energy, Oct. 1956, pp. 55-60, inclusive, and William A. Geyger, in Electronics, May 3, 1963, pp. 58-61, inclusive, present theoretical and practical considerations for the design of certain transformer type multipliers.

Prior art multipliers of the general character here involved have labored under certain disadvantages such as requiring direct current core biasing or presaturating means; requiring special relatively expensive core mate- Patented Sept. 19, 1967 and output, transformer type multiplier with means at the input end for operation from a single phase source, and also by another feature with means at the output end for power factor correction attained essentially by providing inductive and capactive means bridging the output phases. The arrangement is such that only two primary windings per core are required, for some cores but one, in a tripler and closed cores of standard transformer iron are used. There is further contemplated the combination of an inductive load, as an induction motor load, with a transformer type multiplier particularly adapted to such load.

It is a general object of the present invention to obviate or minimize one or more of the above untoward features of the prior art. Another object is the provision of a closed core transformer type magnetic frequency multiplier adapted to provide a multi-phase output having a frequency which is an integral odd multiple of the input frequency, and adapted for operation from a single phase source. Another object is the provision of a multiplier of the described type including means in the output circuity adapted to provide power factor correction among the output phases and an improvement in the output wave shapes. A further object is the provision of a transformer type multiplier wherein there is a good utilization of core material and having an economical coil requirement and arrangement. Other objects and advantages of the invention will appear from the following detailed description and from the drawings wherein:

FIG. 1 is a schematic diagram showing one embodiment of the invention;

FIG. 2 for clarity shows separately and by a different drawing arrangement the connection pattern of the secondary windings of FIG. 1;

FIG. 3 is a graphical showing of the output performance characteristics of a multiplier as shown in FIG. 1;

FIG. 4 is a diagram showing pulsing sequence for the several cores; and

FIG. 5 is a diagram showing the composition of pulses to provide the three output phases of FIG. 1, being correlated in time with FIG. 4 vertically aligned thereabove, though not in area.

A preferred form of the invention for a tripler, shown by the schematic circuit of the drawing, is adapted to be energized from a single phase source, for example, cycle alternating current, with provisions for receiving energization from nominal 110, 220, or 440 volt power lines and includes further means for a finer adaptation to a source actually differing somewhat in voltage from any of the nominal voltages so stated. The form of the invention here disclosed has a three-phase, cycle, nominally 220 volt output.

The primary components are an auto transformer T including a principal winding 10 and auxiliary winding 11, an inductor L-1, and three delta connected capacitors C-a, C-b and C-c, comprising a network for the input circuitry; six transformer type reactors, T-l to T-6, specifically comprising the frequency multiplying network; and a load power factor correcting network connected to the three phase output, comprised of the three Y-connected inductors Lx, L-y and L-z, having capacitors C-x, C-y and C-z, connected in series respectively therewith and to corresponding output lines leading to the distinct output terminals x, y and z for respective phases, there being also a neutral terminal N. Also there is shown an inductive load M on the output as hereinafter detailed.

T-l, T-3 and T-5 are of one type of construction and winding, and T-Z, T4, and T-6 are of a second type, designated respectively Type I and Type II, as indicated by the applied Roman numerals. It is to be observed that each reactor has two primary windings with terminals designated 1-2, 3-4, and two secondary windings with terminals designated 5-6, 7-8.

In the input, with a usual auto-transformer arrangement, one end of the principal winding 10 is connected to the input terminal and to line 27 as one side of the single phase output of the transformer; and the other end to line 28 as the other side of the single phase output and also to the terminal 24 as a selective point for the second line from the source, to be used for a nominal 440 volt source. The winding has intermediate taps to terminals 21 and 22 for selective connection of the second input line for 110 or 220 volt sources respectively. The auxiliary winding 11 has terminals 25 and 26.

One corner of the delta connection or network of capacitors C-a, C-b, C-c is connected to the transformer output line 27, another corner through the choke inductor L-l shuntable by switch S to the transformer output line 28, and the capacitor network output is applied by the lines 31, 32, and 33, connected respectively to the corners, to the frequency multiplying network proper.

When the source voltage is close to one of the nominal input voltages for which the transformer is tapped, auxiliary winding 11 is not used, as it is intended by appropriate connection to provide an additive or bucking 20 volts to compensate for off nominal source voltages. L-1 is connected in the manner shown and just described where the input to the auto transformer is a nominal line voltage. When the line voltage is low, auxiliary terminal 25 is connected to terminal 24 and terminal 26 of the auxiliary winding provides (in place of 28) the output connection to the inductor L-l; while, for a line voltage higher than nominal for a tap to be used, the auxiliary winding 11 is reversely connected between 24 and the inductor L-I, that is, terminal 26 to terminal 24, and terminal 25 as the output to L-l, in this providing a bucking voltage.

Among the six reactors or transformers, T-1 to T-6, the secondary windings having terminals 7-8 are all connected in series, but with alternating polarity, between the neutral terminal N and one of the phase output terminals Z. The other three secondary windings designated by terminals 5-6 of the Type I transformers and those of Type II are connected in respective series between the neutral terminal and each of the other phase terminals Y and X. This provides a Scott T connection as shown more clearly in FIG. 2.

Primary windings of T-1 to T-6, in three series groups as will be described, are Y-connected as the input of the frequency multiplier proper to the three lines 31, 32 and 33. Thus from line 31 to a common line G at the center of the Y are connected the primary winding 3-4 of the Type II reactor T-2, the winding 1-2 and the winding 3-4 in Type I reactor T-3, and the winding 1-2 in Type II reactor T-4; from 32 to G, the winding 3-4 in Type II reactor T-4, the windings \1-2 and 3-4 in Type I reactor T-S, and winding 1-2 in Type II reactor T-6; between line 33 and G, the windings 1-2 and 3-4 in Type I reactor T-1, winding 1-2 in Type II reactor T-2 and winding 3-4 in Type II reactor T-6; the polarities being as indicated by the dots. Thus it is seen that in each branch of the Y-connected input arrangement there are connected in series the two windings of a Type I reactor, and a single winding from each of two Type II reactors. In the Type I reactors, windings 1-2 and 3-4 are effectively a single winding, but are indicated separately since these coils are conveniently so wound on each core leg to obtain uniform saturation.

In a specific example of an embodiment of the invention, the transformers T-1 to T-6 were of generally similar construction with primary 1-2 and secondary 5-6 wound successively onto one leg and primary 3-4 and secondary 7-8 similarly wound on the like other leg of a hollow rectangular laminated core of good grade ordinary transformer iron, No. 9 and No. 12 AWG copper wire being used for primaries and secondaries respectively. For Type I each primary had 64 turns, in effect a single 128 turn winding, each in Type II 76 turns; while all the 5-6 secondaries had 5 8 turns and the 7-8 secondaries had 29, or one half the turns of 5-6.

In such a single phase to three phase multiplier having the nominal volt input and 220 volt output voltages and frequencies, where L-1 had a reactance of 20 ohms; the capacitors C-a, C-b, C-c, capacitances of 45, 90 and 60 microfarads respectively; the output inductors values of 5 millihenries each and the output capacitors C-x, C-y, C-z, capacitances of 30, 60 and 40 microfarads respectively, good performance and regulation was obtained with various loading on the output, e.g. a range of 242 volts to 204 volts from a non-loaded condition to a load of 9 amperes in one output phase with an induction motor M as the load. 7

Actually the network comprising capacitors C-a, C-b, C-c, serves under operating conditions to supply the magnetizing currents that saturate the cores in the multiplier, not for phase splitting in the true sense even though these currents differ in phase, for if this network is disconnected from the multiplier transformer array, it does not produce a three phase output at leads 3'1, 32, 33. g

The magnetizing current for the reactors provided by the input network capacitors is proportional to the maximum output current obtainable from the secondary windings, hence to the power rating of the apparatus, so that the maximum output power is dependent upon the capacitor and magnetizing currents.

The choke serves as a linear buffer reactor to decouple the apparatus from the line, and under proper operating conditions the current through the choke is at a minimum and supplied at unity power factor, supplying only losses and load power.

Although the transformer or reactor primaries can be fed directly by three phase lines, it has been found that relatively poor performance results; the reactive magnetizing power for saturating the cores is approximately three times the rating for the unit as shown; highly distorted current harmonics are reflected into the line; and any variation in line voltage has a marked adverse effect.

Where the star or Y-connected primaries of closed core reactors are connected to a single phase source through the input network in the combination shown, an effectively three phase symmetrical excitation is provided for the reactor group. As is known, under these conditions for group of p units, each excited p from a preceding unit by a source voltage sufficient to cause saturation, each will unsaturate for an interval 180/p twice each cycle of the exciting or line frequency. It will be noted that the ratio of turns in each primary winding of Type II reactors to the total turns used as the primary of the Type I reactors is substantially about an axis 90 from the phase voltage. Polyphase.

source voltage is absorbed by each reactor as it unsaturates for the stated interval to appear thereon as substantially or practically a rectangular pulse.

In FIG. 4, there are shown for each reactor as designated at the left the time occurrence of voltage pulses appearing on each winding or coil thereof over the span of equal time intervals 1-12 inclusive, that span representing the time of a single cycle of the 60 c.p.s. or 360 for the input used, or 1080 on the 180 c.p.s. basis.

The diagram in FIG. 4 indicates the order in which the cores become and are unsaturated, thereby developing a corresponding pulse, each pulse interval corresponding to the interval in which the flux in the reactor under consideration passes from re to 1%. The pulse duration therefore is determined by the interval of unsaturation, while the amplitude is dependent upon the number of turns of the winding whereon the pulse appears or is measured. It will be observed that over the first halfcycle of the 60 c.p.s. input, in each successive interval (30 duration on input basis) the cores successively pass from saturation in one direction of magnetization to saturation in the other, giving rise to the successive timed pulses in each, and similarly in the second-half cycle with the change of saturations successfully in the opposite directions of magnetization, pulses of opposite polarity are successively generated in each interval for successive reactors.

The pulse diagrams of FIG. 5 on a similar time basis and having corresponding intervals aligned with those of FIG. 4, represent the manner of combination of pulses to obtain a three phase output. Whereas within FIG. 5 the four diagrams are related on a similar area basis, the actual diagrammatical representations as between FIG. 4 and FIG. 5 are not so related, and further only approximations of the pulse shapes for the steady state condition on the basis of the 60 c.p.s. input; or as actually indicated by the legends, 90 On an 180 c.p.s. basis. With the ZN phase pulse amplitudes one-half those of the X-Y phase (e.g., as established by the 1:2 turns ratio of the 7-8 secondaries as compared with the 5-6 secondaries), there results from the T connection a three-phase output across XY, Y-Z and ZX with 120 phase displacement as shown. The occurrence of the 5-6 secondary windings for successive reactors alternately on opposite sides of the node point N in the X-Y phase gives this result.

For a quintupler a similar arrangement of Zn or ten cores would be used with twenty 18 pulse intervals, each representing 90 on the output basis; and so on.

The vertical axes are drawn through each pulse or wave of each phase at a location where the time-voltage areas on opposite sides of the respective axis are equal, and for the described relative amplitudes of the component pulses, analysis shows that axes so located are spaced from phase to phase by 120, and further the areas for each half-cycle wave form are equal among the phases.

Particularly for energizing a load, such as an induction motor, for which not the actual wave shape but rather the time-voltage area is of importance, the output in practical effect is the equivalent of a three phase sine wave output by virtue of the 120 spacing of the axes, and the equal half-cycle average values of voltage. Hence the combination of a three phase induction motor M as the load on the multiplier represents a quite useful and advantageous combination of a three phase induction or synchronous motor, for like flux changes are produced in each phase of the induction motor, with minimized level of flux harmonics in the motor stator-rotor air gaps.

Although the voltage regulation of the multiplier without the output network (FIG. 3, curve A) is good until rather near the current capacity of the multiplier, for a resistive load current I or other load with power factor near unity, with a lagging power factor or inductive load (curve B) the output voltage V drops off markedly with increase of load current I Because of the rather large starting current for induction motor starting, therefore a heavy inductive load, the output voltage drop would diminish the starting torque of a motor energized by the multiplier.

Though power factor correcting capacitors could be incorporated, e.g., in series between the multiplier output and motor for cancelling the internal impedance of the multiplier and load, causing the output voltage to rise with increasing load current (curve C), this approach gives rise to undesired ferroresonance between the inductive load and capacitors, or capacitors and multiplier. A preferred solution is the use of the described output network comprised of the capacitor-choke series, which are star connected across the multiplier output. At the output frequency these inductors are small enough to have an effect upon the capacitor reactances which is small but increasing at higher frequencies so as to counteract the de creasing capacitor path impedances at higher frequencies, thereby forcing multiplier and motor to operate stably. Slightly unequal values are used not only for these capacitors, but also for the chokes for which nominal 5 mh. values were given, to aid in balancing the three phase voltages and currents under certain operating conditions.

Also the previously described shunting switch S is useful for shunting out the buffer inductance L-l on motor starting increasing the available current to reduce motor starting time. Thereafter switch S is opened to restore the function of L-1, eliminating ferroresonating tendency of the multiplier and presenting to the line a load of proper power factor.

I claim:

1. A magnetic frequency tripler comprising six closed iron core transformer-like reactors including three of each of two reactor types, each reactor having a first secondary winding and a second secondary winding and no more than two primary windings, the first secondaries of the reactors being equal to each other in numbers of turns, and the second secondaries of the reactors being equal to each other in numbers of turns, a first type of said reactors having one primary winding, the second type of said reactors having two primary windings like to each other, the ratio of the turns of one primary of the second type reactor to the turns of the primary in a first type reactor being substantially equal to 1/ (2 cos said primaries being connected in three saturable and star-connected series sets of three primaries symmetrically excited by an alternating current source of frequency 1, each said series set comprising the primary of a respective first type reactor and a primary of each of two distinct second type reactors, whereby in each input half-cycle .an output pulse of 30 duration is provided on the secondaries of successively different reactors, with the polarity of said pulses reversing on each said half-cycle for each reactor;

the first secondaries and second secondaries of said reactors being connected in respective series with polarities selected to provide an output in each said series of secondaries, with pairs of consecutive said output pulses, the pulses of each pair of like sign, the pairs successively alternating in sign, the pulse pairs of the two series being offset in time by the duration of one said output pulse whereby first and second output phases of 3 frequency are provided as a two phase output system.

2. A tripler as described in claim 1 wherein the turns ratio of the said first secondaries to the said second secondaries is so selected that the pulse amplitude of the one output phase is equal to that of the second.

3. A tripler as described in claim 1 wherein the turns ratio of the said first secondaries to the said second secondaries is so selected that the pulse amplitude of one series is unequal to that in the other.

4. A tripler as described in claim 1 wherein the first secondaries have half the number of turns of the second, the series of first secondaries is connected to ,a midor node-point of the second series in a Scott type connection, in the second series the secondaries of the first and second type reactors being on respective sides of the node, thereby to provide a three phase output.

5. A tripler as described in claim 1, with an input network comprised of three delta connected capacitors with the said series sets connected to the delta corners, two corners connected to single phase alternating current input lines.

6. A tripler as described in claim including a buffer reactor in one of said input lines.

7. A tripler as described in claim 4, with an input network comprised of three delta connected capacitors with the said series sets connected to delta corners, two corners connected to single phase alternating current input lines.

8. A tripler as described in claim 7 including a buffer reactor in one of said input lines.

9. A tripler as described in claim 4 with a power factor correcting output network comprising three capacitor-inductor series branches star-connected to the three phase output.

10. A tripler as described in claim 9 wherein said capacitors and inductors have unbalanced values; said inductors of relatively small impedance at the intended operating output frequency.

11. A tripler as described in claim 7 with a power factor correcting output network comprising three capacitorinductor series branches star-connected to the three phase output.

12. A tripler as described in claim 8 with a power factor correcting output network comprising three capacitorinductor series branches star-connected to the three phase output.

13. A tripler as described in claim 1, in combination with a polyphase motor presenting an induction motor type of loading energized by the tripler output.

14. A tripler as described in claim 4, in combination with a polyphase induction motor energized by the tripler output.

15. A tripler as described in claim 6, in combination with a polyphase induction motor energized by the tripler output.

16. The combination as described in claim 15, having a buffer reactor shunting switch for the motor starting period.

17. A tripler as described in claim 7, in combination with a polyphase induction motor energized by the tripler output.

18. A tripler as described in claim 8, in combination with a polyphase induction motor energized by the tripler output.

19. The combination as described in claim 18, having a buffer reactor shunting switch for the motor starting period.

20. A tripler as described in claim 10, in combination with a polyphase induction motor energized by the tripler output.

21. A tripler as described in claim 11, in combination with a polyphase induction motor energized by the tripler output.

22. A tripler as described in claim 12, in combination with a polyphase induction motor energized by the tripler output.

23. The combination as described in claim 22, having a buffer reactor shunting switch for the motor starting period.

References Cited UNITED STATES PATENTS 2,437,093 3/1948 Huge 32168 2,727,199 12/1955 Ogle 318-231 2,777,983 1/1957 Kummel 321-57 XR 2,849,674 8/1958 Biringer 32168 2,894,195 7/1959 Genuit 32168 XR ORIS L. RADER, Primary Examiner.

G. Z. RUBINSON, Assistant Examiner. 

1. A MAGNETIC FREQUENCY TRIPLER COMPRISING SIX CLOSED IRON CORE TRANSFORMER-LIKE REACTORS INCLUDING THREE OF EACH OF TWO REACTOR TYPES, EACH REACTOR HAVING A FIRST SECONDARY WINDING AND A SECOND SECONDARY WINDING AND NO MORE THAN TWO PRIMARY WINDINGS, THE FIRST SECONDARIES OF THE REACTORS BEING EQUAL TO EACH OTHER IN NUMBERS OF TURNS, AND THE SECOND SECONDARIES OF THE REACTORS BEING EQUAL TO EACH OTHER IN NUMBERS OF TURNS, A FIRST TYPE OF SAID REACTORS HAVING ONE PRIMARY WINDING, THE SECOND TYPE OF SAID REACTORS HAVING TWO PRIMARY WINDINGS LIKE TO EACH OTHER, THE RATIO OF THE TURNS OF ONE PRIMARY OF THE SECOND TYPE REACTOR TO THE TURNS OF THE PRIMARY IN A FIRST TYPE REACTOR BEING SUBSTANTIALLY EQUAL TO 1/(2 COS 30*); SAID PRIMARIES BEING CONNECTED IN THREE SATURABLE AND STAR-CONNECTED SERIES SETS OF THE THREE PRIMARIES SYMMETRICALLY EXCITED BY AN ALTERNATING CURRENT SOURCE OF FREQUENCY F, EACH SAID SERIES SET COMPRISING THE PRIMARY OF A RESPECTIVE FIRST TYPE REACTOR AND A PRIMARY OF EACH OF TWO DISTINCT SECOND TYPE REACTORS, WHEREBY IN EACH INPUT HALF-CYCLE AND OUTPUT PULSE OF 30* DURATION IS PROVIDED ON THE SECONDARIES OF SUCCESSIVELY DIFFERENT REACTORS, WITH THE POLARITY OF SAID PULSES REVERSING ON EACH SAID HALF-CYCLE FOR EACH REACTOR; THE FIRST SECONDARIES AND SECOND SECONDARIES OF SAID REACTORS BEING CONNECTED IN RESPECTIVE SERIES WITH POLARITIES SELECTED TO PROVIDE AN OUTPUT IN EACH SAID SERIES OF SECONDARIES, WITH PAIRS OF CONSECUTIVE SAID OUTPUT PULSES, THE PULSES OF EACH PAIR OF LIKE SIGN, THE PAIRS SUCCESSIVELY ALTERNATING IN SIGN, THE PULSE PAIRS OF THE TWO SERIES BEING OFFSET IN TIME BY THE DURATION OF ONE SAID OUTPUT PULSE WHEREBY FIRST AND SECOND OUTPUT PHASES OF 3F FREQUENCY ARE PROVIDED AS A TWO PHASE OUTPUT SYSTEM. 